"This is a pivotal moment in Michigan's history," Senate Minority Leader Gretchen Whitmer, D-East Lansing, said at a news conference at the Capitol.

"If they declare war on the middle class ... no one should be surprised if the whole environment at the Capitol changes."

Pressure has been building to introduce a right-to-work bill since voters in the Nov. 6 election defeated a union-backed initiative to enshrine collective-bargaining rights in the state constitution. Such a bill would make it illegal to require financial support of a union as a condition of employment.

On Tuesday, Gov. Rick Snyder said right-to-work is now "on the agenda" in Lansing. Before Tuesday, he consistently said the issue was too divisive and not on his agenda.

Snyder said talks with labor groups and others continue and that no decisions have been made on when or whether to proceed with a bill.

Senate and House Democrats would not say what specific actions they would take in an attempt to block it.

"All legal options are on the table to do anything and everything possible to stop this horrific law from coming into effect," said Rep. Tim Greimel, D-Auburn Hills, the incoming House Minority Leader.

Greimel urged Snyder to make a clearer statement about where he stands on right-to-work.

"The governor has been playing hide the ball on this issue for years now," Greimel said. "If he does support it and will sign it into law, people deserve to know."

Late Tuesday, the Michigan AFL-CIO issued a statement urging Snyder and the Legislature to focus on "family-sustaining jobs rather than partisan politics."